4-chloro-2-fluoro-3-methoxyphenylboronic acid (PBA) and 2-(4-chloro-2-fluoro-3-methoxyphenyl)-1,3,2-dioxaborinane (PBE) are useful intermediates in the preparation of 6-(poly-substituted aryl)-4-aminopicolinate compounds and 2-(poly-substituted aryl)-6-amino-4-pyrimidinecarboxylic acid compounds, which are useful as herbicides. PBA may be esterified using 1,3-propanediol to form PBE.
For some operations it would be desirable to be able to efficiently crystallize a 4-chloro-2-fluoro-substituted-phenylboronic acid, like PBA, or a 4-chloro-2-fluoro-3-substituted-phenylboronic acid ester, like PBE. For example, a 4-chloro-2-fluoro-3-substituted-phenylboronic acid ester crystalline solid may be more convenient to store and transport than a 4-chloro-2-fluoro-3-substituted-phenylboronic acid ester solution. Disadvantageously, PBE has a relatively low melting point, which may impair or preclude an efficient crystallization thereof. The PBE melting point is 39-41° C. A need thus remains for a 4-chloro-2-fluoro-3-substituted-phenylboronic acid ester that has a relatively higher melting point and that can be efficiently formed and efficiently used in subsequent processes, such as the production of herbicide intermediates.